Tuesday, November 26, 2013

I did not find a way to install VMWare player on Ubuntu 13.04 - 64 bits. But, I found an archived site having a VMWare player 6.0.0 for ubuntu 64-bits.
To install VMWare 6.0.0, we need to install install VMWare 5.0.3 first and then the automatic update will do the rest for 6.0.0 version. To do that, open a terminal and run the following commands:

Saturday, May 19, 2012

This is not a new post, it is based on Michael G. Noll blog about Running Hadoop on Ubuntu (Single Node)
I will go through the same steps, but I will point out some exceptions/errors you may face.

Because I am a very new user of Ubuntu, this post is mainly targeting the Windows users and they have very primitive knowledge about Linux. I may write some hints in linux which seems very trivial for linux geeks, but it may be fruitful for Windows users.

Moreover, I am assuming that you have enough knowledge about HDFS architecture. You can read this document for more details.

I have used Ubuntu 11.04 and Hadoop 0.20.2.

Prerequisites:

1. Installing Sun JDK 1.6: Installing JDK is a required step to install Hadoop. You can follow the steps in my previous post.

Update
There is another simpler way to install JDK (for example installing JDK 1.7) using the instructions on this post.

2. Adding a dedicated Hadoop system user: You will need a user for hadoop system you will install. To create a new user "hduser" in a group called "hadoop", run the following commands in your terminal:

$sudo addgroup hadoop

$sudo adduser --ingroup hadoop hduser3.Configuring SSH: in Michael Blog, he assumed that the SSH is already installed. But if you didn't install SSH server before, you can run the following command in your terminal: By this command, you will have installed ssh server on your machine, the port is 22 by default.

After this step, you will need to generate SSH key for hduser (and the users you need to administer Hadoop if any) by running the following commands, but you need first to switch to hduser:

$su - hduser$ssh-keygen -t rsa -P ""To be sure that SSH installation is went well, you can open a new terminal and try to create ssh session using hduser by the following command:$ssh localhost

4. Disable IPv6: You will need to disable IP version 6 because Ubuntu is using 0.0.0.0 IP for different Hadoop configurations. You will need to run the following commands using a root account:
$sudo gedit /etc/sysctl.conf

This command will open sysctl.conf in text editor, you can copy the following lines at the end of the file:

#disable ipv6

net.ipv6.conf.all.disable_ipv6 = 1

net.ipv6.conf.default.disable_ipv6 = 1

net.ipv6.conf.lo.disable_ipv6 = 1

You can save the file and close it. If you faced a problem telling you don't have permissions, just remember to run the previous commands by your root account.

These steps required you to reboot your system, but alternatively, you can run the following command to re-initialize the configurations again.

$sudo sysctl -p

To make sure that IPV6 is disabled, you can run the following command:

$cat /proc/sys/net/ipv6/conf/all/disable_ipv6The printed value should be 1, which means that is disabled.

Installing Hadoop

Now we can download Hadoop to begin installation. Go to Apache Downloads and download Hadoop version 0.20.2. To overcome the security issues, you can download the tar file in hduser directory, for example, /home/hduser. Check the following snapshot:

Then you need to extract the tar file and rename the extracted folder to 'hadoop'. Open a new terminal and run the following command:

$ cd /home/hduser

$ sudo tar xzf hadoop-0.20.2.tar.gz

$ sudo mv hadoop-0.20.2 hadoop

Please note if you want to grant access for another hadoop admin user (e.g. hduser2), you have to grant read permission to folder /home/hduser using the following command:

sudo chown -R hduser2:hadoop hadoop

Update $HOME/.bashrc

You will need to update the .bachrc for hduser (and for every user you need to administer Hadoop). To open .bachrc file, you will need to open it as root:

$sudo gedit /home/hduser/.bashrc

Then you will add the following configurations at the end of .bachrc file

# Set Hadoop-# related environment variables

export HADOOP_HOME=/home/hduser/hadoop

# Set JAVA_HOME (we will also configure JAVA_HOME directly for Hadoop later on)

export JAVA_HOME=/usr/lib/jvm/java-6-sun
# or you can write the following command if you used this post to install your java
# export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_71

# Some convenient aliases and functions for running Hadoop-related commands

unalias fs &> /dev/null

alias fs="hadoop fs"

unalias hls &> /dev/null

alias hls="fs -ls"

# If you have LZO compression enabled in your Hadoop cluster and

# compress job outputs with LZOP (not covered in this tutorial):

# Conveniently inspect an LZOP compressed file from the command

# line; run via:

#

# $ lzohead /hdfs/path/to/lzop/compressed/file.lzo

#

# Requires installed 'lzop' command.

#

lzohead () {

hadoop fs -cat $1 | lzop -dc | head -1000 | less

}

# Add Hadoop bin/ directory to PATH

export PATH=$PATH:$HADOOP_HOME/bin

Hadoop Configuration

Now, we need to configure Hadoop framework on Ubuntu machine. The following are configuration files we can use to do the proper configuration. To know more about hadoop configurations, you can visit this site

hadoop-env.sh

We need only to update the JAVA_HOME variable in this file. Simply you will open this file using a text editor using the following command:

$sudo gedit /home/hduser/hadoop/conf/hadoop-env.sh

Then you will need to change the following line

# export JAVA_HOME=/usr/lib/j2sdk1.5-sun

To

export JAVA_HOME=/usr/lib/jvm/java-6-sun
or you can write the following command if you used this post to install your java
# export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_71

Note: if you faced "Error: JAVA_HOME is not set" Error while starting the services, then you seems that you forgot toe uncomment the previous line (just remove #).

core-site.xml

First, we need to create a temp directory for Hadoop framework. If you need this environment for testing or a quick prototype (e.g. develop simple hadoop programs for your personal test ...), I suggest to create this folder under /home/hduser/ directory, otherwise, you should create this folder in a shared place under shared folder (like /usr/local ...) but you may face some security issues. But to overcome the exceptions that may caused by security (like java.io.IOException), I have created the tmp folder under hduser space.

To create this folder, type the following command:

$ sudo mkdir /home/hduser/tmp

Please note that if you want to make another admin user (e.g. hduser2 in hadoop group), you should grant him a read and write permission on this folder using the following commands:

$ sudo chown hduser2:hadoop /home/hduser/tmp

$ sudo chmod 755 /home/hduser/tmp

Now, we can open hadoop/conf/core-site.xml to edit the hadoop.tmp.dir entry.

We can open the core-site.xml using text editor:

$sudo gedit /home/hduser/hadoop/conf/core-site.xml

Then add the following configurations between <configuration> .. </configuration> xml elements:

<!-- In: conf/core-site.xml -->

<property>

<name>hadoop.tmp.dir</name>

<value>/home/hduser/tmp</value>

<description>A base for other temporary directories.</description>

</property>

<property>

<name>fs.default.name</name>

<value>hdfs://localhost:54310</value>

<description>The name of the default file system. A URI whose

scheme and authority determine the FileSystem implementation. The

uri's scheme determines the config property (fs.SCHEME.impl) naming

the FileSystem implementation class. The uri's authority is used to

determine the host, port, etc. for a filesystem.</description>

</property>

mapred-site.xml

We will open the hadoop/conf/mapred-site.xml using a text editor and add the following configuration values (like core-site.xml)

<!-- In: conf/mapred-site.xml -->

<property>

<name>mapred.job.tracker</name>

<value>localhost:54311</value>

<description>The host and port that the MapReduce job tracker runs

at. If "local", then jobs are run in-process as a single map

and reduce task.

</description>

</property>

hdfs-site.xml

Open hadoop/conf/hdfs-site.xml using a text editor and add the following configurations:

<!-- In: conf/hdfs-site.xml -->

<property>

<name>dfs.replication</name>

<value>1</value>

<description>Default block replication.

The actual number of replications can be specified when the file is created.

The default is used if replication is not specified in create time.

</description>

</property>

Formatting NameNode

You should format the NameNode in your HDFS. You should not do this step when the system is running. It is usually done once at first time of your installation.

Run the following command

$/home/hduser/hadoop/bin/hadoop namenode -format

NameNode Formatting

Starting Hadoop Cluster

You will need to navigate to hadoop/bin directory and run ./start-all.sh script.

Starting Hadoop Services using ./start-all.sh

There is a nice tool called jps. You can use it to ensure that all the services are up.

Using jps tool

Running an Example (Pi Example)

There are many built-in examples. We can run PI estimator example using the following command:

Sunday, May 13, 2012

We
talked about Strings operations in the last article, now we will talk about
more tips on performance tips, we will talk about the importance of creating
stateless methods and class if your logic doesn't depend on the state of the
object, also we will talk about object reusing and how will affect the
performance by reducing the headache of garbage collection.

Take
'State or Stateless' Decision

Creating
and destroying objects issue in java can cause performance issues, for example
creating State classes for stateless data; a stateless class means that the
data of the created object doesn't depend on the state where there is no fields
or attributes that makes an object differs from other.

We can imagine that the Stateless class can say 'Use
me only if your code doesn't depend on your object state, All the objects are
functionally equivalent to me, you will gain besides that no creation of
objects, the CPU will be happy of doing that J'

Code Example

The following StatelessClassWithoutStaticMethods class has a
method called execute, where the logic of this method doesn't depend on the
state of the object, while it is not static method.

package
performancetest.episode2;

publicclass StatelessClassWithoutStaticMethods {

publicvoid execute()

{

// the logic here doesn't depend on
the object state

for (int
i = 0; i < 10000; i++) {

System.out.println(i);

}

}

}

While the right version as the
following:

package
performancetest.episode2;

publicclass StatelessClassWithStaticMethods {

publicstaticvoid
execute()

{

// the logic here doesn't depend on
the object state

for (int
i = 0; i < 10000; i++) {

System.out.println(i);

}

}

}

Performance Analysis

Using TBTB (Eclipse Test & Performance Tools
Platform Project), the following results are shown as follows

Performance Analysis

Based
on this figure, the static execute method has loss approximately 18% of time
from the non-static one.

That
doesn't mean that you have to make all the class a static (i.e. a class has
static methods only), but if you have a state method in this class depends on
the object state, make this method only non-static.

Don't
Create A New One If You Can What You Have

'You
can use me before I go to the garbage collection, clear my data and reuse me
again; we want to lessen the work on our friend garbage collection' Any object
says this quote J, Creating new objects is expensive as we know as more
objects we create, the garbage collection job will be more time consuming.

So if
you have a chance to reuse the object again without creating a new one of the
same type, do it immediately, it will improve the performance and will make the
garbage collection job be easier.

Code
Example

publicstaticvoid
fillVectorDataWithoutRecycling()

{

for (int
i = 0 ; i < 1000 ; i ++)

{

Vector v = newVector();

v.add("item1");

v.add("item2");

v.add("item3");

System.out.println(v.get(0));

}

}

publicstaticvoid
fillVectorDataWithRecycling()

{

Vector v = newVector();

for (int
i = 0 ; i < 1000 ; i ++)

{

v.clear();

v.add("item1");

v.add("item2");

v.add("item3");

System.out.println(v.get(0));

}

}

We have
two methods, fillVectorDataWithoutRecycling method creates a new vector object
in the loop, while fillVectorDataWithRecycling method uses one vector object
and clears the vector object and reuse it.

Performance
Analysis

Performance Analysis With/Without Vector Recycling

From
this figure we found that reusing the current object will cause loss approximately
50% of time (of course without taking in the consideration the hardware
architecture like CPU, cache and memory).

There are some performance tips for String
manipulation in java, one of them is the concatenation operation.

Concatenation operation can be done by
appending the values on the same String object for example:

String str = new String ();
String s = "test";
str+=s;

str+="testString";

The compiler translated this simple line to
the following J

str = (new
StringBuffer()).append(s).append("testString").toString();

But this method is not preferable (as we will
know later), one other method is using StringBuffer .

Using StringBuffer Method

StringBuffer is used to store character
strings that will be changed as we know that String class is immutable, so we
can concatenate the strings as follows:

StringBuffer sbuffer = new StringBuffer();

sbuffer.append("testString");

StringBuffer vs StringBuilder

Also there is another method to concatenate
the String using StringBuilder which is introduced in Java 5, StringBuilder is
like the StringBuffer except it is not synchronized, which means that if there
are many threads, they can change it in the same time (StringBuilder is not
suitable in the multithreading applications).

'Ok, why this stuff for, just for concatenate
some strings!' you may ask this question, after running a sample of each and
profiling the performance.

Code Example

public class StringOperations {

public void concatenateUsingString() {

String str = new String();

for (int i = 0; i < 10000; i++) {

str += "testString";

}

}

public void concatenateUsingStringBuffer()
{

StringBuffer sbuffer = new StringBuffer();

for (int i = 0; i < 10000; i++) {

sbuffer.append("testString");

}

}

public void concatenateUsingStringBuilder()
{

StringBuilder sbuilder = new StringBuilder();

for (int i = 0; i < 10000; i++) {

sbuilder.append("testString");

}

}

}

And in the main method, a simple calling to
the three methods

public static void main(String[] args) {

StringOperations soperations = new StringOperations();

soperations.concatenateUsingString();

soperations.concatenateUsingStringBuffer();

soperations.concatenateUsingStringBuilder();

}

The result is like the following:The Results by seconds

The
Results by percentage

I have used
the Eclipse Test & Performance Tools Platform Project (TPTP) to validate
the results, just right click on the project and choose 'Profile As'.

Then
choose 'ProfileàProfile
Configuration '

Profile Configuration

This result shows the big performance issue of using the
String concatenation (Plus operation),

the profiler tells us that the calling of concatenateUsingStringBuffer and
concatenateUsingStringBuilder (approximately 0.08%) of time are nothing with
respect to concatenateUsingString (99.85% of time).

Friday, May 11, 2012

Installing Sun JDK 1.6: You can download oab-java6 zip file from this URL , then you will need to extract this zip file and open the terminal (pressing ctrl+alt+t) to run ./oab-java6.sh. You must be run this command as sudo (using a root account).

This script is doing the following:

The basic execution steps are:

Remove, my now disabled, Java PPA 'ppa:flexiondotorg/java'.

Install the tools required to build the Java packages.

Create download cache in /var/local/oab/pkg.

Download the i586 and x64 Java install binaries from Oracle. Yes, both are required.